A major objective of this project is to establish genetic relationships, by DNA homology experiments, among broad groups of bacteria isolated from the oral cavities of both normal individuals and those with periodontal disease. The major group of bacteria that will be investigated will be the Bacteroides. Studies will be compared on the B. melaninogenicus, B. asaccharolyticus and B. ruminicola-like groups. DNA homology relationships will be determined among B. oralis-like strains. DNA homology studies among oral Rusobacterium strains will be initiated, as will ecological relationships among F. nucleatum strains. The distribution of plasmids among Bacteroides DNA homology groups will be determined.